Search

A compatible organic/inorganic nanocomposite film for a stretchable resistive memory device with high performance is demonstrated using poly(4-vinylpyridine)-block-poly(propyl methacrylate) (P4VP-b-PPMA) with zinc oxide (ZnO) nanoparticle. The PPMA soft segment is designed for reducing the rigidity of the active layer, while the P4VP block serves as a charge-trapping component to induce conductive filament and also a compatible moiety for inorganic nanoparticles through hydrogen bonding. The experimental results show that the P4VP-b-PPMA-based electrical memory device exhibits write-once-read-many-times memory behavior and an excellent ON/OFF current ratio of over 10 5 with a stable turn-on voltage (V set ) around -2.0 V and stable memory behavior upon stretching up to 60% strain. On the other hand, P4VP-b-PPMA/ZnO nanocomposite film switches the memory characteristic to the dynamic random access memory behavior. The stretchable memory device prepared from the nanocomposite film can have a stretching durability over 40% strain and up to 1000 times cycling stretch-relaxation test. This work demonstrates a new strategy using nanocomposite films with tunable electrical characteristics and enhanced mechanical properties for stretchable electrical devices., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this study, poly(δ-valerolactone) (PVL) axles bearing movable and fixed dibenzo-24-crown-8-ether wheels (rot-M and rot-F) are investigated for the first time in the terms of phase transition and nanoscale film morphology: PVL-rot-M and PVL-rot-F. Interestingly, the PVL axles reveal a strong tendency to form a horizontal lamellar structure with three different rotational crystal lattice domains in nanoscale films. The morphological structural parameters are discernibly varied by the movable and fixed rotaxane wheels. In particular, the rot-M wheel tends to be populated in both the interfacial and amorphous layers. The rot-M wheel is found to significantly influence the phase transition characteristics of the PVL axle because of its movability along the polymer backbone chain. In contrast, the rot-F wheel tends to be more localized in the interfacial layer rather than in the amorphous layer because of its immovability constrained at the polymer chain end. The rot-F wheel causes severe thermal instability in the PVL axle, which can be attributed mainly to the presence of its counter anion (PF 6 - )., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of thermo-responsive copolymers of poly(N-isopropylacrylamide) (PNIPAM) and cellulose were synthesized via atom transfer radical polymerization (ATRP) using N-isopropylacrylamide as the monomer, cellulose acetate as the initiator, and CuCl/tris(2-dimethylaminoethyl)amine (Me6TREN) as a catalytic system. The resulting polymers had a narrow range of polydispersity indexes 1.27-1.37, and molecular weights of 8600-17,300 g mol(-1). Novel functional complexes of cellulose-g-PNIPAM/Eu(III) with excellent thermosensitive and fluorescent properties were then formed by the chelation of copolymers and europium(III) ions. The maximum emission intensity of the complexes at 613 nm was enhanced by a factor of approximately 10 relative to that of the corresponding Eu(III) complexes. Additionally, the lower critical solution temperatures (LCSTs) of cellulose-g-PNIPAM/Eu(III) were slightly greater than those of the copolymers., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Recently, experimental investigations of a class of temperature-responsive polymers tethered to oligooxyethylene side chains terminated with alkyl groups have been conducted. In this study, aqueous solutions of poly(glycidyl ether)s (PGE) with varying numbers of oxyethylene units, poly(methyl(oligooxyethylene)n glycidyl ether) (poly(Me(EO)nGE)), and poly(ethyl(oligooxyethylene)n glycidyl ether) (poly(Et(EO)nGE) (n = 0, 1, and 2) were investigated by all-atom molecular dynamics simulations, focusing on the thermal responses of their chain extensions, the recombination of intrapolymer and polymer–water hydrogen bonds, and water-solvation shells around the alkyl groups. No clear relationship was established between the phase-transition temperature and the polymer-chain extensions unlike the case for the coil–globule transition of poly(N-isopropylacrylamide). However, the temperature response of the first water-solvation shell around the alkyl group exhibited a notable correlation with the phase-transition temperature. In addition, the temperature at which the hydrophobic hydration shell strength around the terminal alkyl group equals the bulk water density ( T CRP ) was slightly lower than the cloud point temperature ( T CLP ) for the methyl-terminated poly(Me(EO)nGE) and slightly higher for the ethyl-terminated poly(Et(EO)nGE). It was concluded that the polymer-chain fluctuation affects the relationship between T CRP and T CLP . [ABSTRACT FROM AUTHOR]

Switchable polymerization holds considerable potential for the synthesis of highly sequence-controlled multiblock. To date, this method has been limited to three-component systems, which enables the straightforward synthesis of multiblock polymers with less than five blocks. Herein, we report a self-switchable polymerization enabled by simple alkali metal carboxylate catalysts that directly polymerize six-component mixtures into multiblock polymers consisting of up to 11 blocks. Without an external trigger, the catalyst polymerization spontaneously connects five catalytic cycles in an orderly manner, involving four anhydride/epoxide ring-opening copolymerizations and one L-lactide ring-opening polymerization, creating a one-step synthetic pathway. Following this autotandem catalysis, reasonable combinations of different catalytic cycles allow the direct preparation of diverse, sequence-controlled, multiblock copolymers even containing various hyperbranched architectures. This method shows considerable promise in the synthesis of sequentially and architecturally complex polymers, with high monomer sequence control that provides the potential for designing materials. Switchable polymerization holds considerable potential for the synthesis of highly sequence-controlled multiblock. Here the authors show a self-switchable polymerization enabled by simple alkali metal carboxylate catalysts that directly polymerize six component mixtures into polymers consisting of up to 11 blocks. [ABSTRACT FROM AUTHOR]

Cesium lead halide perovskite quantum dots (QDs) have drawn extensive attention due to their excellent optical properties. However, their use is limited by poor stability. To enhance their stability, we electrospun perovskite-embedded fibers from composite CsPbX3 (X = Cl, Br, and I) perovskite QDs, blending with three polymers, poly(styrene-butadiene-styrene) (SBS), poly(methyl methacrylate) (PMMA), or polystyrene (PS), for the light-emitting diode (LED) applications. We found that the stretchable CsPbBr3@SBS fibers revealed the highest photoluminescence quantum yield, the CsPbBr3@PMMA fibers demonstrated a high thermal stability, and the CsPbBr3@PS fibers exhibited the best water-resistant stability. The photoluminescence intensity maintained 83% of its initial intensity for more than 3 months in water. Furthermore, the LED devices are manufactured from the blue chips and packaged with the core/shell red and green perovskite-based fibers by using biaxial electrospinning exhibited stable and highly efficient white luminescence. The luminance and efficiency are higher than 400% of the values of multilayered structures. [ABSTRACT FROM AUTHOR]

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled Mn was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with Mn ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10−4 cm2 V−1 s−1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10−4 cm2 V−1 s−1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM). The l‐P3HT:PC71BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC71BM. In addition, an amount of collected electrons in c‐P3HT:PC71BM was greater than that in l‐P3HT:PC71BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 266–271 π‐conjugated cyclic molecules are of interest in molecular engineering and are attractive features for use in organic electronics. Polymer‐based organic solar cells are fabricated from synthesized cyclic poly(3‐hexylthiophene‐2,5‐diyl) and a typical fullerene derivative as donor and acceptor materials, respectively. The cyclic structure affects the electron transport properties of the acceptor in the blend film and improves the power conversion efficiency compared to linear P3HT (4.05% vs 3.23%). [ABSTRACT FROM AUTHOR]

ABSTRACT The ring-opening polymerization (ROP) of β-butyrolactone (β-BL) has been studied using the organocatalysts of diphenyl phosphate (DPP) and bis(4-nitrophenyl) phosphate (BNPP). The controlled ROP of β-BL was achieved using BNPP, whereas that of using DPP was insufficient because of its low acidity. For the BNPP-catalyzed ROP of β-BL, the dual activation property for β-BL and the chain-end models of poly(β-butyrolactone) (PBL) were confirmed by NMR measurements. The optimized polymerization condition for the ROP of β-BL proceeded through an O-acyl cleavage to produce the well-defined PBLs with molecular weights up to 10,650 g mol−1 and relatively narrow polydispersities of 1.19-1.39. Functional initiators were utilized for producing the end-functionalized PBLs with the ethynyl, maleimide, pentafluorophenyl, methacryloyl, and styryl groups. Additionally, the diblock copolymers consisting of the PBL segment with the polyester or polycarbonate segments were prepared by the BNPP-catalyzed ROPs of ε-caprolactone or trimethylene carbonate without quenching. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2032-2039 [ABSTRACT FROM AUTHOR]

The colorimetric detection of anionic species has been studied for α‐amino acid‐conjugated poly(phenylacetylene)s, which were prepared by the polymerization of the ethyl esters of N‐(4‐ethynylphenylsulfonyl)‐L‐alanine, L‐isoleucine, L‐valine, L‐phenylalanine, L‐aspartic acid, and L‐glutamic acid using Rh+(2,5‐norbornadiene)[(η6‐C6H5)B−(C6H5)3] as the catalyst in CHCl3. The one‐handed helical conformations of all the sulfonamide‐functionalized polymers were characterized by Cotton effects in the circular dichroism spectra. The addition of anions with a relatively high basicity, such as tetra‐n‐butylammonium acetate and fluoride, induced drastic changes in both the optical and chiroptical properties. On the other hand, anions with a relatively low basicity, such as tetra‐n‐butylammonium nitrate, azide, and bromide, had essentially no effects on the helical conformation of all the sulfonamide‐functionalized polymers. The anion signaling property of the sulfonamide‐functionalized polymers possessing α‐amino acid moieties was significantly affected by the installed residual amino acid structures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1683–1689, 2010 [ABSTRACT FROM AUTHOR]

The article examines the thermoresponsive property controlled by end-functionalization of poly(N-isopropylacrylamide) (PNIPAM) with phenyl, biphenyl, and triphenyl groups. Using an initiation system, the polymerization of NIPAM was carried out. The effect of the end group is likely to appear for low-weight molecular polymers, so the preparation of the end-functionalized PNIPAM, with a series of hydrophobic groups are targeted. The PNIPAM end-functionalization was shown to be one direct approach to construct the polymer with a tuned thermoresponsive property.

The regio- and stereoselective cyclopolymerization of 1,2:5,6-dianhydrohexitol, 1,2:4,5-dianhydropentitol, and 1,2:5,6-diepithio-1,2:5,6-tetradeoxy-hexitol has been studied as a new synthetic method for preparing artificial carbohydrate polymers lacking an anomeric linkage, quite different from the structure of naturally occurring polysaccharides. The carbohydrate polymers consisting of (1→6)-linked 2,5-anhydrohexitol as five-membered ring units were formed by the cyclopolymerizations of 1,2:5,6-dianhydro-3,4-di-O-alkyl-d-mannitol, -l-iditol, -d-glucitol, and -allitol, while the formation of six-membered ring units was found in a polymer prepared by the cyclopolymerization of 1,2:5,6-dianhydro-3,4-di-O-alkyl-galactitol. In addition, the anionic cyclopolymerization of 1,2:5,6-dianhydrohexitol produced a well-defined carbohydrate polymer. The cationic cyclopolymerization of 1,2:4,5-dianhydro-3-O-methylxylitol proceeded regio- and stereoselectively to produce a novel carbohydrate polymer consisting of mainly (2→5)-linked 1,4-anhydro-3-O-methyl-dl-arabinitol as five-membered ring units. The cationic and anionic cyclopolymerizations of 1,2:5,6-diepithio-1,2,5,6-tetradeoxy-3,4-di-O-methyl-d-mannitol and 1,2:5,6-diepithio-1,2,5,6-tetradeoxy-3,4-di-O-methyl-l-iditol were a novel method for producing sulfur-containing carbohydrate polymers, i.e. thiosugar polymers. These carbohydrate polymers acted as a macromolecular ionophore, which exhibited size-selective cation-binding ability for metal cations and chiral discrimination ability for racemic amino acid derivatives. They were applied to optical resolution systems as liquid and solid membranes and, chiral stationary phase in HPLC. [Copyright &y& Elsevier]

In this study, we investigate structures and stabilities of the micelles of a cyclic amphiphile (c-PBA-b-PEO) composed of poly(n-butyl acrylate) (PBA) and poly(ethylene oxide) (PEO) blocks and its linear diblock and triblock analogues (l-PBA-b-PEO and l-PBA-b-PEO-b-PBA) by using synchrotron X-ray scattering and quantitative data analysis. The comprehensive scattering analysis gives details and insights to the micellar architecture through structural parameters. Furthermore, this analysis provides direct clues for structural stabilities in micelles, which can be used as a good guideline to design highly stable micelles. Interestingly, in water, all topological polymers are found to form ellipsoidal micelles rather than spherical micelles; more interestingly, the cyclic polymer and its linear triblock analog make oblate-ellipsoidal micelles while the linear diblock analog makes a prolate-ellipsoidal micelle. The analysis results collectively inform that the cyclic topology enables more compact micelle formation as well as provides a positive impact on the micellar structural integrity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermoresponsive block polyglycidylethers are expected to be used as biomaterials. • MD simulations of two polymer chains have been employed to understand the structural transition of thermoresponsive polymers and interpolymer arrangements. Block copolymers are expected to be applied in a wide variety of fields due to the property of self-assembly. Our group has reported that poly(glycidyl ether) block copolymers exhibited complex temperature response in aqueous solution. In this study, we investigated the two chains of the block copolymer structure and configurations at different temperatures by using MD simulation. The results showed that at low temperatures, the polymer structure is linear and can form micelles, but above a certain temperature, the polymer structure changes to a U-shape and the micelle structure would be destroyed, which is responsible for the complex temperature response. [ABSTRACT FROM AUTHOR]

Micelles were prepared in organic solvents by using three topological polymer amphiphiles: (i) cyclic poly(n-decyl glycidyl ether-block-2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether) (c-PDGE-b-PTEGGE) and (ii) its linear analogue (l-PDGE-b-PTEGGE); (iii) linear poly(6-phosphorylcholinehexylthiopropyl glycidyl ether-block-n-dodecanoyl glycidyl ether) (l-PPCGE-b-PDDGE). For the individual micelle solutions, the size and distribution were determined by dynamic light scattering (DLS) and synchrotron X-ray scattering analyses. The synchrotron X-ray scattering analysis further found that c-PDGE-b-PTEGGE forms oblate ellipsoidal micelle in an ethanol/water mixture, l-PDGE-b-PTEGGE makes prolate ellipsoidal micelle in an ethanol/water mixture, and l-PPCGE-b-PDDGE forms cylindrical micelle in chloroform. This comparative study found that there are large differences in the size and distribution results extracted by DLS and X-ray scattering analyses. All possible factors to cause such large differences are discussed. Moreover, a better use of the DLS instrument with keeping its merits is proposed. [ABSTRACT FROM AUTHOR]

In this article, the authors discuss various articles in this issue of the periodical on advanced polymer particles.

In this study, we report for the first time the thin film morphology and property characteristics of a series of adamantane-containing polymers, which were investigated by using synchrotron grazing incidence X-ray scattering, X-ray reflectivity and spectroscopic ellipsometry. The chemically incorporated monomeric and dimeric adamantane units could disturb regular chain packing, ultimately producing amorphous polymers. They further tend to randomize chain orientations even in nanoscale thin films; surprisingly, random chain orientations could be achieved even for thermally-annealed thin films, which are quite different from the in-plane orientations of conventional polymer films being enhanced by thermal annealing. As a result, isotropic optical refractive indices and dielectric constants could be demonstrated even in nanoscale thin films, which are highly demanded for the production of advanced microelectronic devices. Moreover, the adamantane units incorporated into the backbone and as primary side groups could significantly reduce the dielectric constant, refractive index, critical angle, electron density and mass density of polymer. Overall, the positive impacts of incorporated adamantane units are huge on the polymer morphology and properties. All adamantane-containing polymers of this study are suitable materials for advanced microelectronics, which can replace current workhorse dielectrics, such as silicon oxide, silicon nitride, and polyimides, being used in microelectronic devices. Image 1 • Adamantane moieties incorporated in polymer disturb chain packing order severely. • Adamantane units randomize chain orientation even in thermal-annealed thin films. • Adamantane moieties produce zero or near zero birefringence of nanoscale films. • Adamantane units lead zero or near zero anisotropy of dielectric constant of films. [ABSTRACT FROM AUTHOR]

• Poly(phenylacetylene) bearing Boc-L-valine pendants was successfully synthesized. • Various morphological assemblies were produced by tuning the volume fraction of solvent. • The chirality of supramolecular assemblies could be controlled by a heating–cooling process. A challenging aim is the precisely controlled construction of hierarchical chiral self-assembly in synthetic polymers both from the fundamental and advanced technological development perspectives. Amphiphilic polymers can be assembled into well-organized aggregates with morphological varieties, and external stimuli remarkably affect their self-assembly behavior. We designed and synthesized an amphiphilic helical poly(phenylacetylene) homopolymer containing bi-valine pendants. The hierarchical chiral self-assembly behavior of the homopolymer was realized and investigated by adding a polar solvent into the poly (L- 1) solution. Furthermore, the influences of the solvent components and temperature on the supramolecular chirality and morphologies of the ordered nanostructures were studied via circular dichroism (CD), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Various morphologies such as spheres, beads-string micelles, vesicles, nanorods, flower-like, and blocky nanostructures were obtained. The polyphenylacetylene backbone was successfully endowed with chirality from L-Boc-valine pendants, and this property was further transferred and enhanced in high-ordered supramolecular self-assemblies. With the increase of polar solvent fraction, the enhanced driving force of solvophobic interaction and π-π stacking might significantly promote the aggregation of multi micelles. [ABSTRACT FROM AUTHOR]

Abstract: The living ring-opening polymerization of l-lactide was carried out by using organocatalyst to synthesize the molecular weight controlled poly(l-lactide) with an phenylacetylenyl end group (HCh name="sbnd" />PLLA), then the homopolymerization of HCh name="sbnd" />PLLA was performed by using two different rhodium catalysts. Low molecular weight poly-PLLA6-1 (M w,SEC-MALLS =46,700) was synthesized by using Rh(nbd)BPh4 as the catalyst, and higher molecular weight poly-PLLA6-2 (M w,SEC-MALLS =471,000) was synthesized by using the [Rh(nbd)Cl]2/Et3N catalyst system. Then high molecular weight poly-PLLA20, poly-PLLA29, and poly-PLLA68 were successfully synthesized by using the [Rh(nbd)Cl]2/Et3N catalyst system. The α values of the poly-PLLAs using [Rh(nbd)Cl]2/Et3N catalyst system were all in the range of 0.6–0.8, this means that these polymers possess linear flexible chain. It is concluded that [Rh(nbd)Cl]2/Et3N was more suitable for the synthesis of the cylindrical polymer brush, poly-PLLA with high molecular weight. The analyses of the CD spectra indicated that poly-PLLA possesses a predominantly one-handed helical conformation, temperature and solvents had significant influences on the helical structure of poly-PLLA. [Copyright &y& Elsevier]

Abstract: Hyperbranched polythreitol (1) with different molecular weights (M w,SLS: 1.18×104 and 4.79×104) was reacted with trityl chloride in DMF to afford a novel amphiphilic polymer (2) consisting of 1 as the hydrophilic core and the trityl groups as the hydrophobic shell. Compound 2 was tested for its ability to act as a unimolecular nanocapsule toward the water-soluble dye, rose bengal (RB). Their encapsulation and release properties were also evaluated by comparison with the degree of substitution (DS) of the trityl groups, i.e., the hydrophobic shell density. The polymers were found to have very good unimolecular nanocapsule characteristics even at extremely low concentrations. The average number of RBs per polymer molecule depended on the hydrophilic core size and the hydrophobic shell density. The increasing DS value led to a decrease in the encapsulated amount due to the decrease in the hydrophilic core space, while the low DS value (less than ca. 20mol%) led to a destabilization as a unimolecular nanocapsule and a lower encapsulation ability. In particular, 2 with ca. 23% DS value showed an efficient encapsulation. Based on a release test of the RB-loaded unimolecular nanocapsules, the polymers showed a high RB-holding ability in water. [Copyright &y& Elsevier]

Abstract: The synthesis of a novel unimolecular reverse micelle, the hyperbranched d-glucan carbamate (3), was accomplished through the carbamation reaction of the hyperbranched d-glucan (1) with the N-carbonyl l-leucine ethyl ester (2) in pyridine at 100°C. Polymer 3 was soluble in a large variety of organic solvents, such as methanol, acetone, chloroform, and ethyl acetate, and insoluble in water, which remarkably differed from the solubility of 1. The degree of carbamate substitution (DS) for 3 was controlled by the feed rate of 2, and the DS values were in the range of 46.0–93.7%. Polymer 3 possessed the encapsulation ability for water-soluble molecules, such as rose bengal, thymol blue, and alizarin yellow in chloroform, and the encapsulation ability depended on the hydrophilicity of 3 and the molecular size of the dye. The rose bengal (RB) encapsulated polymer (RB/3) showed a slow release from the RB/3 system into water at neutral pH, while the release rate was significantly accelerated by the hydrolysis of the hydrophobic polymer shell under basic conditions. [Copyright &y& Elsevier]

One-handed helical substituted polyacetylene has received extensive attention due to its potential in chiral stationary phases and molecular recognition. Here, three one-handed helical poly(phenylacetylene)s bearing proline or proline dipeptide as the pendants (PPA-Pro, PPA-Pro-Pro and PPA-Pro-Hyp) were synthesized. As the catalyst, the three helical polymers separately catalyzed the asymmetric aldol reaction of acetone with p -nitrobenzaldehyde in a various media. The results indicate that PPA-Pro-Pro and PPA-Pro-Hyp bearing dipeptide pendants showed the higher catalytic activity and enantioselectivity than the PPA-Pro bearing proline pendants and the corresponding monomer catalysts. This indicates the synergistic effect of the dipeptide pendants with the one-handed helical mainchain of the polymer catalyst. The polymer catalysts can be recycled and maintain the catalytic performance after four circles. When imidazole was added to the reaction system, the reaction yield could be efficiently improved without affecting the enantioselectivity. Unlabelled Image [ABSTRACT FROM AUTHOR]